Streets with a history of multiple people killed or seriously injured in traffic crashes over five years may have underlying safety risks that are likely to recur. Examining crash history by travel mode provides a basis for understanding the existing risks on the street. Even when “speed” or “speeding” is not listed on a crash report, speed may be an underlying factor; speeding is underreported in US traffic crashes, and speed at crash is not always available. Further, fatal and serious injury crashes involving pedestrians, bicycles, and left turning vehicles often can be addressed in part through speed reduction. Cities should use data about fatal and serious injury crashes (when and where they occurred, and what caused them) to both prioritize projects and make design and engineering decisions.

Short-term crash data can be unreliable, especially for the most serious crashes. Using three to five “before” years of crash data and evaluating how the “after” condition differs will help practitioners draw conclusions about the effectiveness of a safety project. Combining severe injury with fatality data is another way to improve the reliability of crash analysis at the project level.

A five-year history of fatal and serious injury crashes can help practitioners understand the risks already present on a street. Denver uses a dashboard to track and display crashes on the street network. In addition to understanding where crashes happen, cities should also look into why they are happening, and use that to make decisions about street design and project prioritization.